Bi 3G Yagi Antenna for 3G nextG Optus Vodafone SCAM 21dBi 3G nextG Yagi Antenna Telstra Optus Vodafone SCAM fake dodgy 18dBi 3G nextG Yagi Antenna Telstra Optus. Thanks for sharing all your expertise and experiences. I am a new General Class ham wo an Elmer to guide me so I try to research all that I can on the Internet. Sanstitre.jpg' alt='Yagi Antenna Calculator Program' title='Yagi Antenna Calculator Program' />A magnetic loop antenna for HF IW5. EDI Simoneby Peter Parker VK3. YE first appeared in Amateur Radio, December 1. October 1. 99. 7s Novice Notes looked at compact antennas that amateurs use to operate from confined locations. The smallest antenna described for 8. Issuu is a digital publishing platform that makes it simple to publish magazines, catalogs, newspapers, books, and more online. Easily share your publications and get. This article provides all the details needed to build your own. Description. Able to cover all frequencies between 3. MHz, the loop described here is directional, does not require a radial system, and stands just 1. Most parts needed can be purchased at a hardware shop. The antenna can be put together in an afternoon and requires only hand tools to assemble. It should cost less than sixty dollars to build. Shown below is the schematic diagram for the loop. Note that the element is continuous except for a gap at the top across which the variable capacitor is wired. The feedline is connected to the bottom of the loop. Maps For Gps Navigator. Also shown is the physical construction of the antenna. The loop element is 1. To minimise losses, thick aluminium strip is used for the element. At the top of the loop is a high voltage variable capacitor. This is used for adjusting the antenna to the operating frequency. Because of its narrow bandwidth, the tuning is very sharp and a vernier drive has been added to make tuning easier. Dimensions are not particularly critical, provided it is possible to bring the loop to resonance on all operating frequencies with the variable capacitor used. Parts needed. The following materials are required to build the antenna 3 2m lengths of 3x. F high voltage variable capacitor. Dick Smith No P 7. RG5. 8 coaxial cable any length and PL2. Many of the above items can be bought at hardware shops. The main exception is the wide spaced variable capacitor. These are almost unobtainable commercially, though you could try Daycom in Melbourne. Other possible sources include old high power transmitting equipment, hamfests and deceased estates. The exact value of the variable capacitor is not particularly important, provided it is at least about 4. F. The capacitor used in the prototype was a two gang 2. F unit with 2mm spacing between the plates. The gangs were connected together to provide the needed maximum capacitance. If your attempts to obtain a suitable capacitor fail, there is always the possibility of making one. Full construction details appear in DK1. NBs magnetic loop design program details later. Construction. The first step in assembling the loop is to make the wooden cross that supports the aluminium element. This is done by bolting a 1. A white polyethylene chopping board is used for the antennas base. The two right angled brackets are used to attach this to the vertical section. The next step is to bend the three lengths of aluminium so that they form a 1. As is visible in Figure Two, two pieces are L shaped, while the other is bent into a shallow U. Note that the two L shaped pieces are about 1. These are physically joined by the bakelite insulation block that is attached to the top of the length of pine. The upper L shaped pieces meet with the lower U shaped piece at points v and w. The overlap is about 4. Make the electrical connection at these points as good as possible. To achieve this, sand the aluminium at the point of contact and use two or more small bolts to hold the pieces together. Use special conductive paste if available. The variable capacitor is mounted on a home made metal bracket so that its shaft faces downwards. To the shaft is attached a vernier reduction drive. Use either small brackets, fishing line or glue to fasten the frame of the reduction drive to the 1. Note the thick, low resistance conductors between the end of the loop and the tuning capacitors. Braid from a length of coaxial cable was used in the prototype. Make these connections short to minimise losses. The loop is fed at the bottom. The braid of the feedline connects to the centre of the lower horizontal element see diagram, point x. The inner conductor connects to the loop at point y via a 9. At both x and y, a small bolt, nut and eye terminal connector is used to make connections to the aluminium element. The distance between x and y and the length of the coaxial cable may both have to be varied for proper matching this is discussed later. Adjustment. The object of the adjustment process is to adjust the section between x and y until the antennas feedpoint impedance can be made to equal 5. The first step is to connect the antenna to an HF receiver tuned to 7 MHz. Set the receivers RF and AF gain controls to near maximum and the antennas capacitor to minimum capacitance plates fully unmeshed. Then gradually increase the capacitance. Not much will happen at first, but the noise from the receiver should gradually start to increase. Further adjustment of the capacitor will result in the received noise falling. Turn the capacitor back to the position where the noise peaks. Depending on the value of your capacitor, the plates should be around a quarter meshed at this point. This test confirms that the antenna can be tuned to 7 MHz. Repeat the process for 8. This time, the noise should peak when the capacitor is near maximum capacity. If it is not possible to obtain a peak, try setting the receiver to a higher frequency 4 or 5 MHz and tune for a peak. If a peak is obtained there, but not on 3. MHz, it is likely that the variable capacitors maximum capacitance is too low for eighty metres. Possible remedies include substituting a larger capacitor, connecting high voltage fixed capacitors in parallel with the variable capacitor or making the loop larger. Having confirmed that noise peaks can be obtained on all frequencies of interest, it is now time to ensure that the antennas impedance is 5. This entails making adjustment to the antennas feed pont. The use of a resistive antenna bridge is recommended so that you can make antenna measurements without radiating a signal. If all you have is a conventional SWR bridge, make adjustments during the day to minimise the risk of interference to other stations. Position the antenna near its final operating position which should be out of other peoples reach. Set your transceiver to about 3. MHz. Adjust the variable capacitor for maximum received noise. Transmit a steady carrier and note the reflected power or SWR. Adjust the transmitter up and down 4. SWR is lowest. Note the reading at this frequency. If you are lucky, the reflected power should be nearly zero. Otherwise, adjust the length and position of the 9. You will find that there is some interaction between these adjustments and the setting of the variable capacitor. All Nokia Phone Flashing Software. Every time a change has been made, adjust either the transmitting frequency or the antennas variable capacitor for the point where reflected power is lowest. Repeat these procedures until reflected power is either zero or close to it. When making these adjustments, there is a temptation to leave the transmitter keyed while making changes to the antenna or adjusting the variable capacitor. This should not be done for two reasons. The first is that the voltages at the top of the antenna element can be quite high hundreds or even thousands of volts even with quite low transmitting powers. The second is that the loop is detuned when people are near it. Thus any adjustment made when you are near the loop will not be optimum when you move away. This effect is particularly pronounced on higher frequencies, and applies to metal objects as well as humans. Once a length and position for the 9.